Multilayer photographic element having a mixed grain emulsion and process employing it



MULTILAYER PHOTOGRAPHIC ELEMENT HAVING A MIXED GRAIN EMULSION AND PROCESS EMPLOYING IT Filed Feb. 21,1948

Nov. 2, 1948. E. B. KNOTT ETAL. 2,452,765

15 I GREEN JENS/T/VE A; C!

1H. BLUESENSlT/VE INTERNAL LATENT IMAGE EMULSION 13% l2 RED SENi/T/VE .SIL VER HAL/PE 11 Q; l SUPPORT.

COLOR DEVELOPER CONTAIN/ 6 MAGENTA COUPLER "I6 507' NO SILVER HAL/DE SOLVENT J8 MAGENTA or:

M TENT IMAGE OF'BLUE SENS/WON LATENT IMAGE 01' RED .S'ENS'AT/ON cozok- DEVELOPER mum/mm cm/v COUPLER BUT NO SILVER HAL/DEJOLVENT 16- I w H (MAGENTA -DYE J9\ I LATENT IMAGE or 521/: saws/4m Q 0 U v/ @YAN DYE 10 I COLOR DEVELOPER (ONM/N/NG rzuaw COUPLEI? AND SILVER HAL/DE JOLVENT 16 I 20 W a MAGENTA. DYE i n-uow or: 11 Pam/v .DYE

EDWARD B. KNOTT a UY W. w. STEVENS IN V EN TOR-S ATTORNEYS Patented Nov. 2, 1948 MULTILAYER PHOTOGRAPHIC ELEMENT HAVING A MIXED GRAIN EMULSION AND PROCESS EMPLOYING IT Edward B. Knott and Guy William Willis Stevens, Harrow, England, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application February 21, 1948, Serial No. 10,186

In Great Britain September 2, 1942 Claims.

This invention relates to photographic processes and material therefor.

This application is-a continuation-in-part of our application Serial No. 528,738, filed March 30, 1944, now abandoned. I

Various proposals have been made in the past for selectively processing inseparably superposed sensitive silver salt emulsionlayers and sensitive silver salt emulsions mixed in a single layer. Such selective processings have been proposedfor various purposes such as for multi-colour photography or for making numbers of prints of the same contrast from negatives of widely differing contrasts.

As is known the latent photographic image formed by the action of light on a photographic silver halide emulsion is not confined to the surface of the silver halide grains but is also distributed internally throughout those grains. It is possible to develop only the so-called surface latent image by means of developers which have little solvent action for silver halide. One of us has described in the literature given below that after removal of the surface latent image the internal latent image can be developed as simply and conveniently as can an ordinary surface latent image if this is done by employing adeveloper having a solvent action for silver halide;

moreover the image so obtained indicated that the speed of the emulsion as measured by the internal image is often comparable with the speed as measured by the surface developed image. Such a developer is for convenience called an internal developer, and an example of such a developer is given on page 47 of the Phot. J 1942, 82, ,42, The

accompanying drawing showsin sectional view a photographic film at various stages in our process. v I

We have found that there isa type of emulsion, which while known per-se, is of sucha nature that the latent image is formed mostly inside the silver halide grains and that, there is relatively little surface latent image formed; such emulsions have not foundmuch commercial use, in fact they have for a long time been considered as practically useless. In other words, our discovery is that such emulsions can have a considerable commercial use if they are' developed .with an internal developer, sincein that case their effective practical speed as measured byi'the pro- 2 greater than was hitherto suspected. An example of such type of emulsion is that known as Burton's Emulsion given in Walls Photographic Emulsions 1929 pp. 52-53. Moreover this type of emulsion may be prepared in other known manners, for instance by taking an ordinary silver iodobromide emulsion containing between 0.5 and 5% silver iodide (based on the total silver halide), and coating it as a layer and then after drying,

treating it with the following bath:

Potassium bichromate grams 12 Cone, sulphuric acid ccs 12 Water do 1000 15 The time of treatment must be suflicient to inhibit surface latent image formation as can easily be ascertained by exposing (after washing) and then treating with developers of Formulae I and III, given below. Such an emulsion layer can then be used as it is or may be remelted and coated again as desired.

In the present invention we apply the aforesaid discovery to give a very advantageous method of achieving selective processing of closely adjacent emulsions, especially of mixed emulsions, which comprises employing for at least one of the emulsions an emulsion which upon exposure forms the latent image mostly inside the grains and another emulsion which upon exposure forms surface duction of adequate densities is many times Development time 3 minutes at 20 C.

FORMULA II (2)) Internal developer Hydroquinone grarn. 12 N -methylp-aniinophenol sulphate d 3 Sodium sulphite (cryst) do 90 Potassium bromide do 4 Sodium carbonate (cryst) i do l 50 Sodium thiosulphate (oi-yet.) do 20 Water to ccs 1000 Development time 4 minutes at 26 C.

FORMULA III Commercial developer This is the same as Formula l'(b) but omitting th following cording to the invention, should satisfy the following requirements.

As measured according to normal photographic testing technique, when the layer is developer? the internal developer Formula- II(a) the density obtained at any point along the logioE over a range of 3.0 starting fromthe threshold of the curve (D=0.1 above fog), should be atleast 5 times, and preferably at least it times the density obtained when development is done with the surface developer of Formula I, the measurements being made at the corresponding (i e. same) points on the logmEi axis. Although in the above test the Formula I developer is specified the developer of Formula III may be used in place thereof.

For some purposes, such as where a small ex-- :posure range is employed, such as for making a tone correcting mask, the emulsion need not conform to such a rigid requirement but it may be suflicient if in the above test the range of .3.0 is substituted by a'range giving densities of 0.1 to 0.501 of 0.1 to 1.0.

An internal latent image emulsion made described in Davey and Knott U. 53. application ,1

Serial No. 790,232, filed December 6, 1947, may also be used according to our invention. This emulsion is prepared by first forming in the absence of ammonia and in one or more stages silver salt grains consisting at least partly of a.

silver salt which is more soluble in water than silver bromide, subsequently converting the grains "to silver bromide or silver bromoiodide and if the silver iodide content of the emulsion is less than 6% calculated on the total silver halide, treating such grains with an iodine compound to bring the silver iodide up to at least 6%, ripening An example of an emulsion made in this way is as follows:

Solution No. 1

'Iner't gelatin'e 20 gms. K01 2O ems. at-40 C. Water 560 cc.

Solution No. 2

at C.

KCL. Watcn.

Solution N o. 5'

Run Solutions Nos. 2 and 3 simultaneously into Solution No. l in a vessel, taking 9-?) seconds to do this. Then ripen for 1 minute at 45 C. Next add Solution No. 4 then ripen for 20 minutes at 45 C. Next add 235 grams of inert gelatine (dry). Then ripen at 45 C. for 15 minutes during which time the gelatine dissolves. Set and shred the emulsion and then wash until free from all soluble bromide and then add about cc. of 10% solution of KCl (by weight), and then add water to make 3 litres.

An internal latent image type of silver halide emulsion may also be defined as one which, when a'tes't portion is exposed to a light intensity scale for a fixed time between and 1 second, and developed for 4 minutes at 20 C. in the ordinary, surf-ace developer (Formula I), exhibits a maximum densitynot greater than .4 the ma imum density obtained when the same emulsion is equally exposed and developed for 3 minutes at 20 C. in an internal type developer (Formula Ila). Preferably the maximum density obtained with the surface developer is not greater than the maximum density obtained when the same emulsion is developed in the internal type developer. Stated conversely, an internal latent image emulsion, when developed in an internal type developer (Formula Ila) exhibits a maximum density at least 5, and preferably at least 10, times the maximum density obtained when the same'emulsion is exposed in the same way and developed in a surface developer (Formula I).

Type vl'I.-These are the emulsions which will develop normally in Formulae I and III well as in Formulae II(a) and II(b). Most known sensi tive materials comprising a gelatino silver hali i emulsion fall in the categor of type II. By develop normally we mean for 4 minutes at 20 C. to give a density at any point along the logmE axis of the character t curve in the developer of FormulaIIw) which does not exceed the density. at the same point on the loglcE axis when developed in the developer of Formula III.

It is to be noted that internal developer is necessarily capable of developing not only a latent image inside grains but also a latent on the surface of grains.

The present invention provides a useful sensitive photographic material comprising on a single support two sensitive silver salt emulsions one of which upon exposure forms the latent image mostly inside the grains and the other of which upon exposure forms a surface latent image on most of theexposed grains, the combination being such that either such emulsion can be exposed and. then simply developed by treating the whole with a developer without thereby causing a deleterious degree of development in the other.

Whenever it is desired that several emulsions on the same support can each be selectively exposed, this can be done by several known methods, namely:

(ct) Making the emulsions differentially colour sensitive.

(b) If the emulsions are in superimposed layers, placing a light absorbing filter layerbetween them or in one of them such as in the type I emulsion. I

(c) If the emulsions'are side by side (i. e. in different areas of the support) they can be easily exposed separately.

Possible ways of arranging an emulsion of type I and an emulsion of type II in the present invention are illustrated by the following:

(1) A not specially colour sensitized emulsion of type I having a relatively high blue sensitivity mixed with or superimposed on a green or red sensitized emulsionof type II of relatively low blue sensitivity.

(2) A green sensitive emulsion of type I mixed or superimposed on a red sensitive emulsion of type II.

(3) A not specially colour sensitized emulsion of type I coated on a not specially colour sensitized emulsion of type II with a blue absorbing filter layer there-between, or the filtering material may be in one of the emulsions such as in the type I emulsion. Such emulsions can be on the same side or opposite sides of the support.

(4) A type I emulsion, colour sensitized or not and a type II emulsion, colour sensitized or not, coated side by side (i. e. in different areas of the support).

' The invention is not limited to these specific ways which are given by way of example only.

We have found that a useful multi-colour photographic process and sensitive material for use therein results if there is employed on a single support two emulsions of different types in the sense just described. The invention is not limited in its application to colour photography.

The following Example I illustrates a material which can be employed in a two-colour process.

Example I.-To 3,500 cos. of an emulsion of type I (which has not been specially colour sensitized) containing the silver halide equivalent of 200 grams of silver nitrate there is added 200 cos. of an 8% alcoholic solution of hydrolysed soft lac resin (see United States Patent 2,199,978 dated May 7, 1940). To 3,000 cos. of a type II silver chloride emulsion containing the silver chloride equivalent of 60 grams of silver nitrate and sensitized to green by addition of 1'75 cos. of a 0.02% alcoholic solution of the dye of Example III of United States Patent 2,282,116 dated May 5, 1942, there is added 60 cos. of an 8% of alcoholic solution of the said hydrolysed soft lac resin. The two emulsions are then mixed at 30 C. and coated on a support such as paper, or they may be coated as superimposed layers. After exposure to a colour image or object this material can be processed to give a two-colour negative image by employing the procedure described below in Example II except omitting step (2) and using a coupler giving an orange image instead of the coupler giving a yellow image in step (3).

Selective developability depending on latent image distribution may also be usefully combined with known means (see for example United States Patent 2,231,684 dated Feb. 11, 1941) for obtaining selective developability. For instance in a subtractive process of three-colour photography, silver bromide or iodo-bromide emulsion of type II may be mixed with a silver bromide or iodobromide emulsion of type I and a silver chloride emulsion of type II; alternatively these emulsions may be coated in three superimposed layers be selectively developed before the other emulsions are developed. Similarly the use of known controlled penetration means at a convenient stage of the processing may be used to differentiate between two emulsion layers both of the same type coated in superimposed layers one of the emulsions being mixed with a third emulsion of the other type. Protective layers which are only penetrated by suitable acid or alkaline solutions may also be used in the same way.

The following illustrates a three-colour process:

Example II .--On a support, there is first coated a silver bromide or iodobromide emulsion of type II sensitized to the red with, for instance, 3:3 dimethyl-4 5 4 :5-dibenzthiacarbocyanine iodide. Over the layer so formed there is coated a mixture of a silver chloride emulsion (type II) sensitized to the green with a sensitizing dye hav ing little or no tendency to wander (e. g. the dye of Example III of United States Patent 2,282,116 dated May 5, 1942) and an emulsion of type I of silver iodobromide sensitive only to the blue. This type I emulsion is one which absorbs blue light very strongly and this has the effect of reducing considerably the effective blue sensitivity of the red sensitive layer; alternatively this blue sensitivity can be effectively reduced in known manner by interposing a yellow filter layer between it and the other emulsions. The blue sensitivity of the silver chloride emulsion is so low that there is practically no image formed therein when the blue sensitive emulsion mixed therewith is properly exposed. This mixture may be made exactly as the mixture prescribed in Example I. The two emulsions of the mixture may if desired be coated as superimposed layers.

After exposure of the material to a coloured object or image, it is processed as follows:

(1) Treat in a mildly acting first developer such as Formula XIII in United States Patent 2,059,884 dated Nov. 3, 1936, containing a colour coupler which gives a magenta coloured image,

for a time just sufiicient to colour develop the silver chloride emulsion without having any practical effect on the silver bromide (see for instance British specification. No. 500,826).

(2) After washing. develop in a developer containing a coupler giving a blue-green coloured image for sufficient time to develop only but completely the image in the lower red sensitive emulsion layer (type II emulsion).

(3) After again washing, develop in a developer containing a coupler giving a yellow coloured image, such developer containing also a silver halide solvent, such as 5 to 4.0 grams per litre of sodium thiosulphate, so as to develop the image in the silver iodobromide emulsion (type I) in the upper layer.

(4) After washing dissolve out all silver formed and all unused silver halides in a bath of sodium thiosulphate and potassium ferricyanide.

A less advantageous form of the invention is illustrated by the following example:

Example III.A film support is coated with a high contrast fine grain process type emulsion,

layer is treated for 3 hours at F. in the following solution.

Potassium dichromate grams l2 Sulphuric acid (conc.) ccs 12 Water to make ccs 1,000

HQ It is then washed for 5 minutes in running water. and then treated for 2 minutes at 70 F. in:

Sodium bicarbonate "grams" 50 Water to make ccs 1,000

A final thirty minutes washing is then. given and the layer is dried.

This treatment converts, the process emulsion from type II to type I. The other side of the film is then successively coated with a blue absorbing filter layer and then an emulsion of type II. This material can be used for a two colour process as a printing material where it is desired to expose both emulsions prior to any processing step.

Our invention will now be described by reference to the accompanying drawing. As shown in the drawing, a support I is coated with a silver bromide or iodobromide emulsion I I, of type II containing red-sensitive silver'halide grains I2. Over this layer there is coated a single emulsion layer I 3 containing a mixture of green-sensitive silver chloride grains I4 and blue-sensitive silver iodobrornide grains I5 of type I. After ex posure of this material to a colored object or image, it is processed as shown in the remaining stages of the drawing.

As shown in the second stage of the drawing, the sensitive element after exposure is treated with a mildly acting developer containing a magenta coupler but no silver halide solvent to form a magenta dye image I6 in emulsion layer I3 leaving' a latent image I! of the red sensation in emulsion layer II and a latent image I8 of the blue sensation in emulsion layer I3.

The element is then subjected to the action of a color developer containing a cyan coupler but no silver halide solvent for a time sufilcient to develop a cyan dye image I9 in emulsion layer I I as shown in the third stage of the drawing. After again washing, the element is developed in a developing solution containing a yellow coupler and also containing a silver halide solvent, to form yellow dye image as shown in the fourth stage of the drawing. All silver and unused silver halide are then removed.

Other examples of the use and selective treatment of emulsions of difierent types on a single support are as follows, and in these examples the emulsions may be also differentially colour sensitized so that they can be exposed selectively by different coloured lights.

(a) Side by side stereoscopic images (i. e. on different areas of the support) produced on the same cinematograph film which are to be de-:

veloped to red and green respectively (for viewing through red and green spectacles) may be processed in a simple manner by treatment of the whole film first with a developing solution for developing only one of the emulsions (and subsequently with a developing solution for developing the other emulsion).

(.b) A picture image and a sound track image can be developed separately without the trouble of applying the development solutions to the separate picture and sound areas of the cinematograph film (e. g. by applicator rollers) by employing (e. g. in admixture) an emulsion of one type for printing the sound track and an emulsion or emulsions of the other types for printing the picture.

(0) Where it may be desirable to develop the two longitudinal halves of 16 mm. film separately, for example, one half to black and, white and the other to a coloured image ior any purpose; this 8 can be done by adopting a procedure analogous to that indicated in (a) and (b).

Although the invention which has been described above requires that the emulsions of types I and II should be so arranged that either of them can be exposed and simply developed by treating the whole with a developer without thereby causing a deleterious degree of development in the other, it is possible to modify the above invention by dispensing with this requirement and making the emulsions so that they give widely differing gammas and then such a material, although less useful than those previously described, can be used for so-called multi-contrast purposes, such as for producing images of different contrasts from negatives of the same contrast or images of the same contrast from negatives of different contrasts.

A sensitive material for this purpose can be made by mixing in one layer or coating in superposed layers two emulsions giving widely differing gradations, one of the emulsions being of one of the above types and the other of another of the above types. Such emulsions can be dye-sensitized or not. As an example we can employ an emulsion of type II giving a low gradation in Formula III and an emulsion of type I giving a high gradation in Formula II (b). In this combination the threshold speed of type II emulsion when developed in developer Formula II or III should for example be higher than that of type I emulsion when developed in developer Formula II (b) preferably the characteristic curves under these conditions should cross at about a density of one.

The material so made can be printed with white light and then the contrast of the image controlled by choice of the developer. For example using an emulsion of type II giving a low gradation and an emulsion of type I giving a high gradation, the image will be of relatively low contrast if developed in a developer such as Formula III, or relatively medium contrast in a developer of Formula IIb, and of high contrast if then first treated in a mild silveroxidizing bath which destroys surface latent images in ordinary emulsions of type II and then developed in Formula IIb.

Two examples of such solutions are the following solutions A and B.

Solution A Potassium Ierricyanide grams 20 Potassium bromide do 10 Water to ccs 1,000

Solution B Potassium dichromate grams 2 Cone sulphuric acid ccs 2 Water to ccs 1,000

As another example, the threshold speed of the type II emulsion can be equal or lower than that of the type I emulsion. Such a material gives low contrast mainly due to the type II emulsion on development in Formula III and a high con trast mainly due to the type I emulsion on development in Formula II(a) or 11(1)).

It will be understood that our invention is to be taken as limited only by the scope of the appended claims.

We claim:

1. A sensitive photographic element comprising a support having thereon two superposed emulsion layers, one of which layers is a red sensitive silver halide emulsion (II) a test portion of which upon exposure to light and development for 4 minutes at 20 C1. in the following developer (11b);

Grains Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4 Sodium carbonate, crystals 150 Sodium thiosulfate, crystals 20 Water to 1000 ccs.

gives a density along the logmE. axis of the characteristic curve which does not exceed the density at the same point along the logmE axis obtained when an identical test portion of the light-sensitive silver halide emulsion (II) is exposed and developed for 4 minutes at 20 C. in the following developer (III):

Grams Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4 Sodium carbonate, crystals 150 Grams Hydroquinone 15 N-methyl-p-aminophenol sulfate 15 Sodium sulfite, anhydrous 50 Potassium bromide 10- Sodium hydroxide 25- Sodium thiosulfate, crystals 20 Water to 1000 ccs.

gives a maximum density at least 5 times the maximum density obtained when the equally exposed identical silver halide emulsion is developed for 4 minutes at 20 C. in the following surface developer (I):

Grams p-I-Iydroxyphenylglycine Sodium carbonate 100 Water to 1000 00s.

2. A sensitive photographic element comprising a support having thereon two superposed emulsion layers, one of which layers is a red sensitive silver bromide emulsion (II) a test portion of which upon exposure to light and development for 4 minutes at 20 C. in the following developer (IIb) Grams Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4 Sodium carbonate, crystals 150' Sodium thiosulfate, crystals 20 Water to 1000 ccs.

givesa density along the logmE axis of the characteristic curve which does not exceed the density at the same point along the logioE axis obtained when an identical test portion of the light-sensitive silver halide emulsion (II) isexposed and developed for 4 minutes at 20 C. in the following developer (III) v Grams Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals Potassium bromide 4 Sodium carbonate, crystals 150 Water to 1000 ccs.

and the other of which layers is a mixture of emulsions, one being a green sensitive silver chloride emulsion of the type (II) specified above, and the other a blue sensitive silver iodobromide emulsion (I) a test portion of which last-mentioned emulsion upon exposure to a light intensity scale for a fixed time between l/ and 1 second and development for 3 minutes at 20 C. in the following developer (Ha):

I Grams Hydroquinone 15 N-methyl-p-aminophenol sulfate 15 Sodium sulfite, anhydrous 50 Potassium bromide 10 Sodium hydroxide 25 Sodium thiosulfate, crystals 20 Water to 1000 ccs.

gives a maximum density at least 5 times the maximum density obtained when the equally exposed identical silver halide emulsion is developed for 4 minutes at 20 C. in the following surface developer (I):

I Grams p-Hydroxyphenylglycine 10 Sodium carbonate Waterto 1000 ccs. 1

3. A sensitive photographic element comprising a suppor-t having on one side thereof two super posed emulsion layers, the layer adjacent the support being a red sensitive silver bromide emulsion (II) a test portion of which upon exposure to light and development for 4 minutes at 20C. in the following developer (IIb) Grams I-Iydroquinone 12 N methyl-p-aminophenol sulfate 3 Sodium sulfi-te, crystals 90 Potassium bromide 4 Sodium carbonate, crystals Sodium thiosulfate, crystals 20 Water to 1000 ccs.

gives a density along the logmE axis of the characteristic curve which does not exceed the density at the same point along the logioE axis ob tained when an identical test portion of the light-sensitive silver halide emulsion (II) is exposed and developed for 4 minutes at 20 C. in the following-developer (III) Grams Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4- Sodium carbonate, crystals e 150 and the outermost layer comprising a mixture of emulsions, one being a green sensitive silver chloride emulsion of the type (II) specified above, and the other a blue sensitive silver iodobromide emulsion (I) atest portion of which last-mentioned emulsion upon exposure to a light intena sity scale for a fixed time between 1/100 and l 11 second and development for 3 minutes at 20 C. in the following developer (IIa):

Grams Hydroquinone 1'5 N-methyl-p-aminophenol sulfate Sodium sulfite, anhydrous 50 Potassium bromide 10- Sodium hydroxide 25 Sodium thiosulfate, crystals Water to 1000 ccs.

gives a maximum density at least 5 times the maximum density obtained when the equally exposed identical silver halide emulsion is developed for 4 minutes at 20 C. in the following surface developer (I):

p-Hydroxyphenylglycine Sodium carbonate 100 Water to 1000 cos.

4. The method of forming a colored image in a multi-color photographic element comprising a support having thereon two superposed emulsion layers, one of which layers is a red sensitive silver bromide emulsion (II) a test portion of which upon exposure to light and development for 4 minutes at 20 C. in the following developer (IIb) Grams Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4 Sodium carbonate, crystals 150 Sodium thiosulfate, crystals 20 Water to 1000 ccs.

gives a density along the logmE axis of the characteristic curve which does not exceed the density at the same point along the logioE axis obtained when an identical test portion of the light-sensitive silver halide emulsion (II) is exposed and developed for 4 minutes at 20 C. in the following developer (III) Grams Hydroquinone 12 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4 Sodium carbonate, crystals 150 Water to 1000 ccs.

Grams Hydroquinone 15 N-methyl-p-aminophenol sulfate 15 Sodium sulfite, anhydrous 50 Potassium bromide 10 Sodium hydroxide Sodium thiosulfate, crystals 20 Water to 1000 ccs.

gives a maximum density at least 5 times the maximum density obtained when the equally exposed identical silver halide emulsion is developed for 4 minutes at 20 C. in the following surface developer (I) Grams p-Hydroxyphenylglycine 10 Sodium carbonate Water to 1000 ccs.

comprising exposing said element to a colored object, developing a magenta colored image in said silver chloride emulsion with a coupling developer containin a color coupler but free of silver halide solvent, for a time just sufficient to develop the silver chloride emulsion without having any effect on the other emulsions, developing a cyan image in the red sensitive emulsion layer with a coupling developer containing a color coupler but free of silver halide solvent, for a sufficient time to develop only but completely the image in the red sensitive emulsion layer, and then developing a yellow image in the remaining emulsion with a coupling developer containing a color coupler and from 5 to 40 grams per liter of a silver halide solvent.

5. The method of forming a colored image in a multi-color photographic element comprising a support having thereon tWo superposed emulsion layers, one of which layers is a red sensitive silver bromide emulsion (II) a test portion of which upon exposure to light and development for 4 minutes at 20 C. in the following developer (IIb) Grams Hydroquinone 1'2 N-methyl-p-aminophenol sulfate 3 Sodium sulfite, crystals 90 Potassium bromide 4 Sodium carbonate, crystals Sodium thiosulfate, crystals 20 Water to 1000 005.

gives a density along the logmE axis of the characteristic curve which does not exceed the density at the same point along the logmE axis obtained when an identical test portion of the light-sensitive silver halide emulsion (II) is exposed and developed for '4 minutes at 20 C. in the following developer (III):

. Grams Hydroquinone 1 12 N-met-hyl-p-aminophenol sulfate 3 Sodium sulfite, crystals I 90 Potassium bromide 4 Sodium carbonate, crystals 1 150 Water to 1000 ccs.

and the other of which layers is a mixture of emulsions, one being a green sensitive silver chloride emulsion of the type (II) specified above, and the other a blue sensitive silver 'iodobromide emulsion (I) a test portion of which last-mentioned emulsion upon exposure to a light intensity scale for a fixed time between 1/100 and 1 second and development for 3 minutes at 20 C. in the following developer (IIa):

Grams Hydroquinone -7 15 N-methyl-p-arhinophenol sulfate 15 Sodium sulfite, anhydrous 50 Potassium bromide 10 Sodium hydroxide I I Ia -I III I '25 Sodium thiosulfate, crystals "20 Water to 1000 ccs.

gives a maximum density at least -5 times the maximum density obtained when the equally exposed identical silver halide emulsion is developed for 4 minutes at 20 C. in the following surface developer (I) Grams p-Hydroxyphenylglycine 10 Sodium carbonate 100 Water to 1000 ccs.

15 Number time to develop only but completely the image in the silver bromide emulsion layer and then developing a yellow image in the silver iodobromide emulsion with a coupling developer containing a color developer and from 5 to 40 grams per liter of a silver halide solvent.

EDW. B. KNOTT.

GUY WILLIAM WILLIS STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,197,994 Butement Apr. 23, 1940 

